Electrical circuits such as house wiring, industrial controls, and aircraft electrical systems often use relatively high voltages and are capable of supplying high currents, such that electrical faults can be particularly dangerous. An arc fault is one such type of electrical fault, resulting from current discharge from one conductor to another in an electrical circuit.
The arc fault is typically the result of some unintended change in physical configuration between conductors that allows current to either flow through a conducting medium or jump across a nonconductive medium from one conductor to another. One common example is worn or aged insulation around electrical wiring in a home, which allows the house's wiring to contact other house wiring. Similarly, loose connections in an outlet, junction box, or light can allow a circuit wire to become free and move, coming in contact with another conductor and creating an arc fault.
Wiring can also be damaged by sharp objects during insulation,, such as by nicking a wire's insulation during installation or wear as a wire rubs against a sharp edge of a junction box. Various connectors and contacts can also wear and deform, and salt bridges can form between conductors in salty or corrosive environments such as near saltwater. Electrical codes and wiring standards seek to minimize the chances of such arc faults occurring, but they remain a significant source of damage to electrical systems and their environments.
These arc faults are the root cause of a number of industrial, residential, and aircraft accidents, particularly in electrical distribution systems. It is therefore important to be able to detect arc faults in electrical systems such as power distribution systems, so that the damage done can be regulated.
Overcurrent regulators such as traditional circuit breakers and fuses can't handle all arc faults, because the fault currents are often within the normal current range of the circuit breaker or fuse. Sparks jumping from one conductor to another, for example, can have relatively little current despite near-constant sparking or arcing. Similarly, as insulation between two conductors becomes worn, the contact area between conductors is very small at first and low-current arcs jump between conductors. Similarly, normal arcs are common in a variety of setting including home and residential, as a result of motors starting, capacitors charging, and other such spikes in current draw in a circuit.
This illustrates the need for a method for accurately detecting arc faults in an electrical circuit, even at relatively low current levels.